Method and apparatus for measuring constituents of gases



Aug. 3l, 1948. A. L. NlcoLAl IETHOD AND APPARATUS .FOR IEASURIHG CONSTITUENTS 0F GASES wwwa EL'ESS IWI? PETENT ORNEY Patented Aug. 31, I

S y PATENT OFFICE METHOD AND APPARATUS FOR MEASURING CONSTITUENT S F GASES Arduo Lewis Nicolai, New York, N. Y. Application my 5, 1945, serai No. 592,131 z claims. (c1. 11s-11:3)

This invention relates to measuring the constituents of gases and particularly to an improved method and instrument for determining the completeness of combustion of fuels by measurement of the products of combustion.

One method for determining the completeness of combustion of fuels is to measure the carbon dioxide in the products of combustion from the burned fuel. For greater accuracy, further measurements are made of the carbon monoxide and oxygen present in the products of combustion. These measurements are necessarily made by chemical analysis and involve complex apparatus and intermittent readings. More recently measurements only of the amount of oxygen present in the products of combustion of fuels have been used as a measure of the excess air present and these are considered better indications of any carbon monoxide present than is the measurement of carbon dioxide.

One method of determining the oxygen present is to measure the increase in the carbon dioxide in the products of combustion as a result of burning the oxygen with some additional fuel. In this methodl should there be any carbon monoxide, hydrogen or methane present in the original products of combustion, an error is introbility, much as permeability which is'common in electrical design, is indicative of the ease with which magnetic lines of force pass through a substance. In general, the greater the susceptibility of a substance, the more readily do the lines go through it. Relative to air, the susceptibility of another gas may be either positive or negative. Oxygen, when placed in a magnetic iield, behaves very differently from other gases usually found in the same sample of products oi combustion of a fuel.

The following table derived from The Handbook of Chemistry and Physics by C. D. Hodgman, pages 1454 to 1464 lishing Co., Cleveland, Ohio, 1936) lists the molecular susceptibilities at ordinary room temperature of the various gases found in products of combustion. 1

Principal constituents of iluegases:

Gas Mclal Susceptibility Oxygen +3395Xl0-c-g.s.eleetromagnetieunits. Carbon dioxide -l8.62 l0 c. g. s. electro-magnetic illll S. Nitrogen -9.68X10c.g.s electro-magneticnnits. Watervapor -l2.58i ts10 c. g. s. electro-magnetic v un duced which in magnitude is proportional to the amount of these unburned combustible products present. When analyzing the products of combustion from furnaces, this error may introduce a considerable inaccuracy in the results obtained.

The invention contemplates the measurement of the constituents of 'a gas by determining the magnetic susceptibility of the gas. In determining the completeness of combustion of fuels this unique method involves subjecting nue gases to a magnetic field and measuring and indicating on a suitable scale the deilection of a container for the gas that is caused by passage of magnetic lines of force through the gas. In the form of apparatus described'herein the measurements of the gases are continuous although intermittent measurements of samples of the gases may be carried out.

Figures 1 and 2 are charts showing the magnetic susceptibility of products of combustion in relation to excess air and oxygen respectively in the products.

Figure 3 is a diagrammatic representation vof apparatus for obtaining a continuous indication in accordance withthe invention.

Figure 4 is a section on line 4 4 of Fig. 3l

It is an established fact that all substances possess magnetic properties. One of these properties is the magnetic susceptibili Suscepti- Minor constituents of flue gases:

Molal Susceptibility Meth 104.

(Value unknown, but believed negative).

ane Carbon Monoxideproducts of different fuels is of a negligible char-- acter.

The susceptibility of a mixture of gases is computed in a finding the specific heat of the same mixture. If O2, CO2, N2 and H2O represent per cent by volume of the constituents in a flue gas and X1, Xa, 2h, and X4 are the respective molal susceptibilities, the molal susceptibility of the mixture is:

(Chemical Rubber Pub- Noteworthy is manner analogous to that used for- I have found that the same molal susceptibilities of said mixtures, and in addition their corresponding volume susceptibilities, when plotted against percentage of O2 by volume in the products, as shown in Fig. 2, result in a remarkably straight line. This is due to the predominant efrect which the oxygen component has in Equation 1 because of its much higher susceptibility. Therefore, it may be deduced from Fig. 2 that the magnetic susceptibility of a flue gas is directly proportional to the percent oxygen by volume present.

. It has been found that if a tube, such as tube 25 (Fig. 3), is lled withgas and suspended between the poles of an electromagnet at right angles to the lines of force, it will experience a force acting in an upward direction.

where K1=volume susceptibility of combustion products, c. g. s. units; Kz=susceptibility of surrounding air=30 10*9 c. g. s. units; a=cross sectional area, of tube cm2; H=eld strength, gausses.

To produce this force F, the field strength is made negligible toward the top of the tube, and increases uniformly to maximum near the bottom. The direction of the force will be upward if the term (K1-K2) is negative, as in the case of combustion products. A glance at Equation 2 will reveal that if K2, a and H are maintained constant, F will vary in direct proportion to K1. I have already shown in Fig. 2 that K1 is proportional to the O2 present. The resultant conclusion is that the force acting on a tube containing flue gases and placed in a magnetic field is directly proportional to the percent O2 in the flue gases.

K2 will remain constant so long as the temperature of the air surrounding the tube is held normal at say 68 F.; a cannot be varied without changing the tube dimensions be kept constant.

In the embodiment of the invention shown in Figs. 3 and 4 the magnet comprises an iron core I8 having two gaps I9 and 20 and an iron piece 2| intermediate the gaps. The gaps each have an expanding portion formed by the beveled sides 22 and 23 on the ends of the core I8 and intermediate piece '2| respectively. The expanding portions on the two gaps face in opposite directions so that the directions of weakening mag-- netic lines of the respective elds are arranged in opposite directions, upwardly on the'left and downwardly on the right. The tube containing the products of combustion is divided into two equal branches 24 and 25 each branch being placed within one of the gaps and therein subjected toV the magnetic field set up by the'core. V-The branches are supported by bearings 26 and 21, located midway between them. The branches -areinterconnected near bearing 21 for` series flow of. gas passed into, through and out of the tube `from 1 the end adjacent bearing 21 in the .directions shown by the arrows. Since the magneticeld gradients are arranged in opposite directions .they

and H can readily' will create forces within the two branches of the tube in opposite directions and thereby will impart a rotating motion to the tube around its bearings. A compensating coil spring 28 may resist the rotation of the tube and a pointer 29 may be attached for indicating the oxygen or excess air reading on a graduated scale 30. The core I8 may be provided with coils through which an electric current may be passed to create magnetic flow through the core. 4The pointer 29 moves along scale 30 in proportion to force F, and if the gas within tube 24, 25 represents the products of combustion of a fuel, the force F will be proportional to the oxygen content. Therefore, scale 30 may be graduated to read the percentages of oxygen by volume, or with suitable correcting device, the percent of excess air present in the products of combustion.

My apparatus is substantially instantaneous in indicating by novel means the oxygen present in 4the products of combustion, may be made to read continuously or intermittently by contro1 of the electric current to the magnet and may be arranged to be recorded by means well known in that art.

While I have shown and described specific embodiments of my invention, it will be understood Ithat many changes in construction, combination and arrangement of parts may be made, and the invention may be applied to other gases than the products of combustion of fuels where similar relations of the magnet-ic susceptibilities of their constituents prevail, without departing from the spirit and scope of the invention as claimed.

What I claim is:

1. Apparatus for measuring the volumetric oxygen content in the gaseous products of combustion of yfuels comprising; electro magnet means having spaced poles and an intermediate member provided with opposed bevelled end faces forming a pair of spaced gaps expanding in directions opposite to each other and at right angles tothe lines of magnetic force; a conduit arranged lto conduct the products serially through the gaps in opposite direction-s and at right angles to the lines ofmagnetic force; means for introducing the products to and taking them from the conduit; means supporting the conduit for rotation means associated with the lconduit for resisting its rotation within the gaps; and means associated with 'the conduit'for indicating its extent of rotation within the gap and thereby the proportion of oxygen in the products.

2. Apparatus for measuring the volumetric OXY- gen content in'the gaseous products of combu-stion of fuels comprising means for producing a. magnetic field, separated pole p ieces forming a gap in said eld and having opposed faces whose separation progressively increasesI in 'a direction substantially normal to the flow of magnetic force lines through the gap whereby the gaps magnetic eld lintensity progressively diminishes in that di- '65 rection, a conduit positioned vin said gap with its -axis substantially normalboth to said magnetic force lines and to said direction of the magnetic elds diminishing intensity, means for passing seid combustion products through sa'id conduit in lthe magnetic eld whereby to subject them to a displacing force that urges them and the conduit in said direction with an intensity which varies directlywith the volumetric oxygen content of the products and which is substantially independent of the remaining ingredients in the products,

:resilient means allowing said'conduit te move in 8 said direction through l. distance wtilch varies UNITED STATES PATENTS with said dispiaeinx force intensity. an means for Number me M measuring seid distance whereby to indicate the 2 174m ma i Oct. 3 1939 mmm "f me n he mm maw th 213001336 Bamm-: li." .oct. 2v: 1942 1 mhmngguo m com 5 z .aszu rem es 4x. Nv.14. 1944 2,418,344 Pulling Rab. 25, 1947 REFEBENclS CITED OTHER REFERENCES The followingr references are of record in the "Magnetic Phenomena." by Williams, page; 9 4

me of this patent: l to a9. Pubmed by McGraw-'mn Book c o. 

